This invention relates to the metering of volumes of liquid in general and more particularly to an improved control system for carrying out such metering.
Metering systems are known in which a counter which is driven by flow proportional signals is used to obtain an actual value of the flow which has taken place. Such devices use the counter output to compare with a set desired value and to terminate flow when the counter reaches the preset desired value. Such devices in which a lead value in order to obtain coarse and fine metering for driving a control element which reduces flow and for also driving a control element to stop flow are also known. Apparatus of this type is described in the journal ATM J122-7.
A problem with this known apparatus is that the magnitude of electrical voltages and currents required for its operation do not permit its use in an environment where there is an explosion hazard. Thus, there is need for an improved apparatus of this nature which permits operating in such an environment.